Space instruments, such as satellites, are normally equipped with a certain number of lengthening pieces able to be deployed, namely solar generators, antenna reflectors, poles, etc. Throughout the satellite launching phase, these lengthening pieces are kept in a folded back position so as to firstly reduce the spatial requirement and secondly avoid damaging them. The keeping of the lengthening pieces in this folded back position is ensured by stacking devices constituted, for example, by bolts traversing the various panels constituting each solar generator.
When the satellite is placed into orbit, pyrotechnic shears are triggered so as to cut the stacking bolts and to free the solar generators or similar lengthening pieces. The actual deployment is then ensured by elastic members mounted on the hinges which each connect panels of the solar generator.
These elastic members are usually constituted by torsional springs which exert between adjacent panels a relatively high deployment torque. So as to ensure that excessive impacts do not occur after deployment, it is necessary to regulate the speed for deploying the panels.
To this effect, cable deployment regulators are normally used which include a coil mounted on a shaft connected to a centrifugal brake by a speed multiplier mechanism. A cable, initially wound onto the coil, is secured via its extremity onto the lengthening piece whose deployment is to be regulated. When deployment of the lengthening piece is triggered, the cable is unwound from the coil and the latter drives in rotation, at a speed increased by the speed multiplier, the rotary feeders of the centrifugal brake. Friction blocks integral with these feeders then come into contact with a stationary track, which has the effect of adjusting the speed of rotation and accordingly adjusting deployment of the lengthening piece.
In such a cable deployment regulator, a braided metallic cable is normally used having a bending rigidity which tends to spontaneously bring it back to the almost rectilinear state, and thus to unwind it from a coil in the free state. For this reason, the coil on which the cable is intially wound is normally placed inside a housing which also contains the centrifugal brake and the speed multiplier mechanism. However, given the fact that it is esential to have a certain amount of play between the cable and the housing, the bending rigidity of the cable tends to make the volume of the latter swell on the coil when this coil is blocked and when any significant tension is exerted on the cable. In the most unfavorable conditions, such a volume swell may result in the cable jamming and the lengthening piece not being deployed. When this lengthening piece is a solar generator, this may thus result in the equipment embarked on the satellite being totally unusable.
In practice, the risks mentioned above are that much more likely when the mechanisms for deploying lengthening pieces equipping satellites are tested a number of times before the satellite is sent into space. In fact, it is necessary after each of these tests to rewind the cable onto the coil through a small outlet window of the cable formed in the housing, that is virtually without any visibility.
As regards equipment functioning on the ground, it has already been envisaged to keep a captive cable on a coil by means of a glue which does not prevent unwinding of the cable as and when desired. This technique is in particular used in certain cases so as to ensure the keeping in a coiled position the wire connecting a wire-guided missile to the ground.
However, this technique has a certain number of drawbacks which render it virtually unusable in certain spheres and especially in spatial applications. Thus, the presence of glue, some of whose particles are pulled up at the moment of deployment, would be unacceptable in spatial applications as it would result in depositing pollutive particles on the large number of optical and other types of instruments equipping satellites. In addition, the cable for regulating deployment moves on pulleys and the presence of glue particles on this cable would risk the latter jamming. In addition, the extreme temperature conditions sustained by the various devices equipping spatial instruments (temperature variation of between about -170.degree. C. and 100.degree. C.) would result in changing the characteristics of all existing glues.